Organic reactions that proceed in aqueous medium without the use of organic solvents have been attracting attention from the viewpoint of environmental care. However, various disadvantages existed for the use of aqueous medium for organic reactions, causing the procedure to be considered difficult. The first main disadvantage is that organic compounds are mostly insoluble in water; the second main disadvantage is that most reaction intermediates and reagents such as catalysts are decomposed by even a trace of water.
The inventors have reported Lewis acid-surfactant-combined catalysts (LASC: e.g., Japanese Patent Application No. 10-53075), which enable various organic synthesis methods such as aldol reaction, allylation reaction, Mannich reaction and Michael reaction in aqueous mediums. Although such Lewis acid-surfactant-combined catalysts is important in that they can give products with relatively high yield and selectivity, higher catalytic activity was desired for aldol reaction in water.
Organic reactions using boron enolates have been well-known as a method for providing products in high selectivity. However, a stoichiometric amount of the boron source was required in previously reported organic reactions using boron enolates, and an organic reaction method using a catalytic amount of boron source that can give the product in high yield and selectivity has not been known.
Accordingly, the present invention has been accomplished in view of the above circumstances, and thus, an object of the invention is to solve the problems of the prior technologies, thereby providing a method for aldol reaction in water, which uses a catalytic amount of boron source and gives the product in high yield and selectivity.